Todoist for Outlook
The installation program has run for more than an hour. Does installation take a very long time or is the file damaged?
The installation shouldn't take more than 30 seconds. If you don't have Microsoft .NET Framework installed, though, it will try to install it and this could take a couple of minutes at most.
Please try to redownload the installer file, save it on your computer, then right-click on it and choose "Run as Administrator".
Also, could you please clarify what happens exactly during the installation - is it stuck on one certain screen, does the progress bar move?